Non-chrome passivation of steel
View Patent ↗Chromate free treatments and compositions for applying a conversion or passivation coating to metal surfaces. Preferred compositions comprise a film forming latex polymer, fluoacid, phosphoric acid, and a polyoxyethylene/oxypropylene block copolymer. The requisite metal surfaces are contacted by the compositions and dried. Rinsing is optional.
1. A method of forming a conversion or passivation coating on a metal surface comprising contacting said metal surface with a chromate free aqueous treatment composition comprising:
(a) 1-20 wt % of a film forming latex polymer;
(b) 1-40 wt % of a fluoacid;
(c) 1-50 wt % of a phosphoric acid; and
(d) 0.01-15 wt % of a non-ionic polyoxyethylene/polyoxypropylene block copolymer surfactant.
2. A method as recited in claim 1 , wherein said fluoacid comprises a fluoacid of a Group IVB metal.
3. A method as recited in claim 1 , wherein said non-ionic polyoxyethylene/oxypropylene block copolymer comprises a mole ratio of ethylene oxide (EO):propylene oxide (PO) groups of about 1:1-9.
4. A method as recited in claim 3 , wherein said EO:PO molar ratio is about 1:5-9.
5. A method as recited in claim 4 , wherein said non-ionic polyoxyethylene/polyoxypropylene block copolymer has a molecular weight of about 2,000-4,000.
6. A method as recited in claim 1 , wherein said metal surface is a zinc covered metal surface.
7. A method as recited in claim 1 , wherein said metal surface is galvanized steel.
8. A method as recited in claim 1 , wherein said metal surface is aluminum.
9. A method as recited in claim 1 , further comprising drying said metal after said chromate free aqueous treatment composition has been brought into contact with said metal, then painting said metal.
10. A method as recited in claim 1 , wherein the pH of said composition is from about 1 to about 2.
11. A method as recited in claim 1 , wherein said latex polymer comprises an acrylate resin.
12. A method as recited in claim 11 , wherein the acrylate resin comprises butyl acrylate, methyl methacrylate, and methacrylic acid polymers.